排序算法05：归并排序

归并排序（MergeSort)

#include "MergeSort.h"

void Merge(int A[], int Start, int Mid, int End)
{
	int n1 = Mid - Start + 1;
	int n2 = End - Mid;
	int *Left = (int*)malloc(n1 * sizeof(int));
	int *Right = (int*)malloc(n2 * sizeof(int));
	int i, j, k;

	for(i = 0; i < n1; i++)
		Left[i] = A[Start + i];
	for(j = 0; j < n2; j++)
		Right[j] = A[Mid + 1 + j];

	i = j = 0;
	k = Start;
	while(i < n1 && j < n2)
	{
		if(Left[i] < Right[j])
			A[k++] = Left[i++];
		else
			A[k++] = Right[j++];
	}
	while(i < n1)
		A[k++] = Left[i++];
	while(j < n2)
		A[k++] = Right[j++];
}

void MergeSort(int A[], int N, int Start, int End)
{
	int Mid;
	if(Start < End)
	{
		Mid = (Start + End) / 2;
		/*
		printf("sort  (%d-%d, %d-%d) ", Start, Mid, Mid + 1, End);
		for(int c = 0; c < N; c++)
		{
			printf("%d ", A[c]);
		}
		printf("\n");
		*/
		MergeSort(A, N, Start, Mid);
		MergeSort(A, N, Mid + 1, End);
		Merge(A, Start, Mid, End);
		/*
		printf("merge (%d-%d, %d-%d) ", Start, Mid, Mid + 1, End);
		for(int c = 0; c < N; c++)
		{
			printf("%d ", A[c]);
		}
		printf("\n");
		*/
	}
}

耗时 Time = 27ms。